The present invention relates generally to gliding decelerators and more particularly to a new and novel gliding decelerator which includes an assembly for improving the lift to drag ratio associated therewith.
It has been found desirable to airdrop military personnel, supplies and equipment from as great a horizontal distance as possible from the ground impact point in order to reduce vulnerability of the delivery aircraft to ground fire and to increase uncertainty on the part of the enemy as to the location of the landing point. One approach which has been used in furtherance of this objective is to airdrop troops and/or cargo using gliding decelerators (i.e. parachutes). Gliding decelerators typically have a hollow, wing-shaped canopy which, after deployment, stiffens to facilitate gliding over a horizontal distance.
One type of hollow, wing-shaped canopy commonly used in gliding decelerators is known as a ram-air type canopy. Such a canopy typically consists of a plurality of elongated, chord-shaped, sections which are sewn together in a side-by-side arrangement. The sections are hollow, with the respective leading ends thereof being open and the respective tailing ends thereof being closed so that, in the course of the opening of the canopy and the descent, air enters through the leading ends of the sections and inflates the sections, thereby opening the canopy and imparting some stiffness thereto for gliding. Suspension lines are either typically attached to the canopy along the seams of every other section, in which case the sections are referred to as "half-cells," or are attached to the canopy along the seams of each section, in which case the sections are referred to as "cells." For purposes of the present specification and claims, the terms "half-cells" and "cells," when used to refer to these sections of a canopy, will be used interchangeably and synonymously.
Examples of gliding decelerators having ram-air type canopies are disclosed in the following U.S. patents: U.S. Pat. No. 5,169,092, inventor Murakami, issued Dec. 8, 1992; U.S. Pat. No. 4,811,920, inventors Askwith et al., issued Mar. 14, 1989; U.S. Pat. No. 4,470,567, inventor Puskas, issued Sep. 11, 1984; U.S. Pat. No. 4,406,433, inventors Radkey et al., issued Sep. 27, 1983; U.S. Pat. No. Re. 31,205, inventor Jalbert, reissued Apr. 12, 1983; U.S. Pat. No. 4,191,349, inventor Pravaz, issued Mar. 4, 1980; and U.S. Pat. No. 3,724,789, inventor Snyder, issued Apr. 3, 1973.
Other patents of interest include U.S. Pat. No. 5,058,831, inventor Takahashi, issued Oct. 22, 1991; U.S. Pat. No. 4,722,498, inventor Cameron, issued Feb. 2, 1988; U.S. Pat. No. 4,363,458, inventors Jones et al., issued Dec. 14, 1982; and U.S. Pat. No. 3,620,486, inventors Charpentler et al., issued Nov. 16, 1971.
The efficiency with which a canopy glides through the air is largely affected by its lift to drag ratio (L/D). One problem experienced by many wing-shaped canopies, and particularly by ram-air type canopies, is a greater than desired drag. A considerable amount of drag in ram-air type canopies can be traced to their open-leading edge and to a lack of stiffness in the canopies after they have been fully opened. This lack of stiffness, which results in fabric flutter, is caused by fluctuations in the ram-air dynamic pressure needed to maintain the shape of the open leading edge and the half-cells of the canopy as the opened canopy glides through the air. Drag is also caused by the suspension lines used to attach the payload to the canopy.